<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="../../js/vue.js"></script>
  <style>
    .fade-enter-active,
    .fade-leave-active {
      transition: opacity .5s;
    }

    .fade-enter,
    .fade-leave-to {
      opacity: 0;
    }
  </style>
</head>

<body>
  <div id="app">
    <button @click="show=!show">Toggle Button</button>
    <transition name="fade">
      <p v-if="show">hello</p>
    </transition>
  </div>
  
  <script>
    let vm = new Vue({
      el: "#app",
      data: {
        show: false
      }
    });
  </script>
</body>

</html>